| skarn gold-copper deposit often contain Fe,S,Ag,Co,Se,Te,Ga,As,Pb,Zn,Ni,Cr,etc,The tailings produced in the mining process contain a lot of heavy metals,if the tailings are not properly disposed,which will become a major environmental safety hazard.Chromium,chemical symbol Cr,single quality steel gray metal,the Cr elements are mainly in the form of+3 and+6,and relative to the Cr???almost do not produce harmful effect to human body,Cr???harm to the human health,Skin contact may cause sensitivity;More likely to cause genetic defects,inhalation may cause cancer,and there is a lasting risk to the environment.Therefore,it is of great significance to study the occurrence,transfer and transformation of chromium in Mining process and its stability in tailings.Taking a gold-copper mine in hubei province as example,the paper studys on the migration,transformation and stability in flotation system of chromium from the component of this gold-copper sulphide ore.By the total amount of ore tested,chemical morphological analysis of chromium from flotation system,it showed distribution and migration of Cr in flotation system.Using various means including XRD and MLA explained phase constituting,binding configuration,occurrence and dissemination characteristics of Cr in ore.The test results of tailings leaching toxicity and speciation analysis experiment evaluated stability of Cr in tailings.Using Geoaccumulation Index,The potential Ecological Risk to Index and RAC to evaluate the environmental risk of chromium in tailings.The main conclusion is as follows:1.The total amount of chromium and the distribution of chromium elements in flotation system:Chromium is present in the mineral of flotation system;The distribution proportion of the chromium element in the flotation system of the gold copper copper mine is:tailings>sulfur concentrate ore>gold copper concentrate ore>iron concentrate ore>loss.The largest amount of chromium in the tailings was 52.2 percent.According to the total analysis results,in the flotation process,Chromium element through the ore into the flotation system,part of chromium as flotation technology migrated to the concentrate,and most of the chromium is entered the tailings,and a small amount of chrome in floatation wastewater or loss through dust and other forms.2.The distribution of chromium elements in flotation system:?1?The chemical morphological distribution ratio of the chromium elements in raw ore is in turn:Residual Fraction>Acid Soluble Fraction>Reducible Fraction>Oxidative Fraction,which is mainly in Residual Fraction.?2?The chemical morphological distribution ratio of the chromium elements in sulfur concentrate ore is in turn:Acid Soluble Fraction>Residual Fraction>Reducible Fraction>Oxidative Fraction,which is mainly in Acid Soluble Fraction.?3?The chemical morphological distribution ratio of the chromium elements in gold copper concentrate ore is in turn:Residual Fraction>Acid Soluble Fraction>Reducible Fraction>Oxidative Fraction,which is mainly in Residual Fraction.?4?The chemical morphological distribution ratio of the chromium elements in iron concentrate ore is in turn:Acid Soluble Fraction>Residual Fraction>Reducible Fraction>Oxidative Fraction,which is mainly in Acid Soluble Fraction.?5?The chemical morphological distribution ratio of the chromium elements in tailings is in turn:Residual Fraction>Acid Soluble Fraction>Reducible Fraction>Oxidative Fraction,which is mainly in Residual Fraction.It can be seen from the experimental results that the tailings produced by the flotation system are mainly in the form of residuals,After the flotation process,the chromium in the sulfur concentrate and iron concentrate mainly exists in the form of reducible state.The gold and copper concentrate and tailings are mainly in the form of residual state,and the proportion of reducible Cr in gold and copper concentrate is as high as 42.3%,which indicates that the potential activity of Cr in gold and copper concentrates needs to be taken seriously.3.The properties of chrome elements in flotation systems are analyzed,the state of occurrence and the characteristics of the insertion.?1?The results of XRD?1?The results of XRD analysis of the raw ore:The raw ore may have Al2?OH?4CrO4·H2O?Ca4Al2O6?CrO?9·H2O?Ca3?CrO4?2??Fe,Mg??Cr,Fe?2O4?Na8Al6Si6O24CrO4?Na4?CrO4?SO4?Ca3Cr2?SiO4?3?ZnCr0.8Fe1.2O4;Chromium may present+2,+3 and+6 in the raw ore.?2?The results of XRD analysis of the gold copper concentrate ore:The gold copper concentrate ore may have Al2?CrO4?2Cr2O7·3H2O?Ca6Cr2?SO4?3?OH?12·26H2O?Ca5?CrO4?3?OH??CaCrSi4O10?NaCr6?SO4?2?Na6Zn?SO4??Cr O4?3;Chromium may present+2,+3 and+6 in the gold copper concentrate ore.?3?The results of XRD analysis of the sulfur concentrate ore:The sulfur concentrate ore may have Ca4Cr2O6SO3·11H2O?Na0.3CrS2·H2O?NaMgCr?SO4?3?Na6Zn?SO4??CrO4?;Chromium may present+2,+3 in the sulfur concentrate ore.?4?The results of XRD analysis of the iron concentrate ore:The iron concentrate ore may have Ca4Al2Cr0.5O10?SO4?0.5·16H2O?Na2Cr?SO4?2·2H2O?NaMgCr?SO4?3;Chromium may present+2,+3 and+6 in the iron concentrate ore.?5?The results of XRD analysis of the tailings:The tailings may have Na4?CrO4??SO4??NaMgCr?SO4?3;Chromium may present+2,+3 and+6 in the tailings.?2?The results of MLA?1?The results of MLA analysis of the raw ore:The main minerals containing chromium in raw ore dressing system are Andradite,Diopside,ordinary Angle amphibole,grossular,augite and epidote gangue minerals,such as chromium mainly occurs in calciumiron pomegranate stone;Andradite is either complex with Calcite or irregular in Chlorite,Crminerals are embedded in other minerals or are complex with other minerals.?2?The results of MLA analysis of the sulfur concentrate ore:The chromium in sulphur concentrate processing system also mainly exist in the calcium iron garnet,diopside,flash Angle of ordinary stone,grossular,augite and epidote gangue minerals,such as chromium mainly occurs in calcium iron pomegranate stone;Cr minerals are embedded in other minerals or are complex with other minerals.?3?The results of MLA analysis of the Copper concentrate ore:The separation system of chromium in copper concentrate mainly exist in the calcium iron garnet,diopside,flash Angle of ordinary stone,grossular,augite and epidote gangue minerals,such as chromium mainly occurs in diopside stone;Diophane and Chalcopyrite were born.,Chromium minerals are embedded in other minerals or are complex with other minerals.?4?The results of MLA analysis of the tailings:The mineral containing Cr elements in tailings is permeable stone,common hornite,green curtain stone,calcium allogite,calcium ferrologite and other gangue minerals,and chromium is mainly deposited in calcium and iron garnet and calcium and aluminum.It contains a large amount of quartz,and the permeable,and the magnetite of the calcium tetrazite.The chrome-containing minerals in the raw ore follow the process of ore dressing,and part of the mineral goes into the corresponding concentrate with the target mineral,while the other part goes into the tailings with the unexploited gangue mineral.4.Analysis of the stability of chromium in tailings?1?Static eluvial experiment?1?Different particle size of tailings Cr6+distribution in samples:When the particle size is greater than 0.3mm,the content of Cr6+is highest;When the level of granularity is greater than 0.097,the volume of the solution of Cr6+is gradually decreasing,but when the granularity is less than 0.097,the solution of Cr6+is rising;The dissolubility of Cr6+in unscreened time was very different from that of sieve.?2?Optimal solid-liquid ratio experiment:In different solid-fluid ratios,the Cr6+is different.The solubility of Cr6+is much higher than that of leaching phase when the solid solution is larger,namely,when the ratio of tailings and leaching is close.And when the solid-fluid ratio is less than 1:5,as the consolidation ratio increases,the Cr6+is gradually increasing?3?Cr6+in different pH of tailings samples of dissolution:After 24 hours of static,the leaching fluid was weakly alkaline,the pH of the extract was higher,and the dissolution of Cr6+was the largest.When the pH gradually increased,the dissolution of Cr6+gradually decreased.?2?Dynamic leaching experiment?1?The PH value of tailings leachate in different leaching conditions:In the first stage of the solution,the pH of the solution is rapidly increasing to a weak base or alkaline range,and as the time of the liquid is increased,the pH of the filtrate is decreasing;With the increase of leaching time,the overall increase with time decreases gradually.?2?Leaching process,the changing rule of the dissolubility Cr6+:At pH=2 and pH=8?in strong acid or alkali condition?,the dissolubility of Cr 6+is higher than pH=4 and pH=6;When pH=8,the dissolubility of Cr 6+is higher than pH=4,and 6.?3?The toxic leaching experiment of tailings:The mineral processing tailings system after leaching toxicity experiment leaching liquid of the concentration of Cr6+with an average of 0.056 mg/L,is far less than the hazardous waste identification standard Leaching toxicity identification?GB5085.3-2007?,leaching toxicity of standard limit.The tailings stability experiment shows that tailings sample particle size,solid liquid ratio,the ph on the dissolution of a Cr6+has a certain influence,in the environmental risk management of the tailings,to pay attention to the physical properties of tailings before into the library,as far as possible to ensure the tailings dry ventilated,prevent outside into the tailings water,in a timely manner to determine dry heap of tailings in ph,ready to dry under the pile of tailings in mainland seepage prevention,avoid dry stack tailings of dissolution of Cr6+into the soil,cause harm to the environment.5.Environmental risk assessment of chromium in tailings:The accumulative index Igeo<0,Igeo level is 0,and the pollution degree is clean.In the tailings of the flotation system,the effective state and the residues in the tailings are both less than or equal to 40,so the effective state of the chromium in the tailings is less than that of the residue state.The tailings of the flotation system belongs to the risk-free grade in the RAC classification,so the chromium in the flotation system does not harm the environment. |
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